The present invention relates to the combination of two vertical axis Savonius-type rotors and one deflector plate device which serves as an augmentation apparatus for both of the rotors. The deflector plate device considerably increases the power output of both Savonius-type rotors and also improves their self-starting ability and smoothness of operation.
As used in this application, the term "Savonius-type rotor" includes rotors having a shape as generally illustrated in this application, in applicant's patent application Ser. No. 069,405 and in applicant's U.S. Pat. Nos. 4,715,776 and 4,359,311, as well as rotors with two or more blades of the classic Savonius-type, wherein the rotor blades are generally semi-cylindrical in shape. This is in contrast to turbines which have the inner edges of the blades fixed to adjoining blades or to a central core, drum or shaft in such a manner that there can be practically no crossing of the fluid past the inner edges of the blades.
High speed propeller-type turbines have dominated the wind energy field largely because of their relatively high efficiency. Slow speed turbines such as the Savonius vertical axis turbine or the multi-blade horizontal axis windmill used for pumping water have typically been of low efficiency and cannot compete with the high speed propeller type turbines for electrical power production. In addition to other disadvantages, however, there are some places where the high speed propeller-type turbine cannot be installed. For example, such a turbine cannot be placed on top of large area flat buildings because the wind would be too unstable, and also the turbines would be too dangerous. Also, with the high speed turbines, safety is a important consideration, and since metal fatigue is related to the number of stress reverses of high magnitude, it is difficult to predict when a blade may come loose from the turbine.
As indicated in applicant's U.S. Pat. Nos. 4,715,776 and 4,359,311, Savonius-type rotors have well-known problems associated therewith. For example, they have low starting torque when oriented at certain directions and their action is jerky and pulsating under a load.
The Savonius-type rotors disclosed in applicant's U.S. Pat. No. 4,7815,776 and U.S. patent application Ser. No. 069,405 offer many advantages over the prior art rotors in that they exhibit considerably improved efficiency, and considerably better self-starting characteristics. These applications also disclose a deflector plate in combination with the rotor which additionally increases the power output of the rotor assembly. The present invention offers even further advantages over existing Savonius-type rotor assemblies.
The present invention provides the combination of two vertical axis Savonius-type rotors and one deflector plate which serves as an augmentation apparatus for both of the Savonius-type rotors. The two Savonius-type rotors of the present invention can be built much larger than the rotor disclosed in applicant's U.S. application Ser. No. 069,405 because the rotors are mounted on a strong central support structure. The use of two vertical axis Savonius-type rotors along with one deflector plate that augments both of the rotors yields a system that has greater efficiency than any high-speed propeller-type turbine, and rivals the intermediate and small sizes in terms of power production. In addition, the present invention is balanced in yaw so that only a minor torque is necessary to keep the rotors oriented properly with respect to the wind. The two blade Savonius-type rotor used in the present invention is set out in applicant's U.S. Pat. No. 4,715,776 U.S. patent application Ser. No. 069,405, both of which are herein incorporated by reference.